This invention relates to axle shafts for vehicles and more particularly to an assembly having a tubular axle shaft with a flange member fixed at the axially outer end of the shaft.
It is known in the art relating to vehicle axle shafts to form such shafts as one piece forgings to transmit the considerable torque and loads applied at the wheel end of an axle housing. It is also known to utilize two piece axle shafts where a solid shaft is friction welded to a flange hub. Friction welding of a tube assembly to a flange hub has also previously been developed.
The present invention provides an improved form of axle shaft assembly in which a mechanical connection is provided between a tubular shaft and a flange hub mounted on an axially outer open end of the shaft. The assembly includes an end wedge forced into the open end of the shaft and expanding the wall of the shaft to compress the wall into engagement with a central opening in the flange hub to provide for transmission of torque and axial forces between the flange hub and the shaft.
In a preferred embodiment, the outer end of the shaft is expanded and provided with a flared end. The flange hub includes a hub portion which is fitted tightly onto the expanded portion of the shaft and against the flared end. Preferably the flange hub central opening includes a characterized surface with spline like features into which the shaft wall is expanded by insertion of the end wedge so that a mechanical torque transmission connection is provided by expansion of the tube into the recesses between the spline like projections. Other forms of characterized surfaces may also be utilized.
The end wedge preferably extends inward of the flange hub to provide a solid support for the expanded portion of the shaft on which a wheel bearing is mounted. The shaft is preferably laser welded to the flange hub at the inner and outer edges of the hub portion and to a head of the end wedge adjacent the outer end of the hub portion.
The inner end of the shaft may be reduced in diameter, splined and provided with additional features for attaching the inner end to an axle drive assembly, such as a differential gear set. The inner end may be hollow with thickened wall sections or may be compressed to a substantially solid end portion.
The invention provides a novel design and method for mechanically attaching a flange hub to a tubular axle shaft including laser welding of the flange hub to the shaft. Benefits of the design and method include:
1. Use of a generally flat flange hub which is more easily manufactured than conventional one piece axle shaft forgings.
2. Significant weight reduction of the axle due to variable wall thickness tubing which is utilized in place of solid bar stock.
3. Use of a mechanical joint between the flange hub and the axle shaft tube formed in part by an end wedge which deforms the axle tube into spline like features or other characterized surface features on the inner diameter of the flange hub central opening.
4. The use of laser welding for additional positive attachment of the shaft tube to the flange hub and the end wedge.
5. Reduced heat treating cycle time due to the lower mass of the tube and reduced internal stresses from the laser welding process.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.